DR. HOOK- Suck it up: Stay hydrated in the heat

Sweat– or is it perspire? According to the dictionary, both verbs sweat and perspire mean "To excrete perspiration through the pores in the skin." Proper Brits know "Horses sweat; men perspire; but ladies glow." Judy Garland didn't know about glow. She said, "I wish I could just perspire. Unfortunately, I sweat!" Tina Turner sweats so much on stage that she wears clothes that can't get drenched– oh, what's sweat got to do, got to do with it?

Believe it or not, as a teenager, I was a singer. Yes, I'm sure all of you have fallen back in your chairs and are now reading this column on your backs. When I lived in Ohio, I actually got three highest achievement state awards for singing. Call me Andrea Bocelli, Laaa!

I was in a show choir called The Top Twenty. The girls put on showy dresses, and the guys put on tuxedos with dorky ruffled shirts. I looked like Jerry Seinfeld in the "Puffy Shirt" episode.

In this choir, everything was choreographed– which meant I was constantly swaying, dancing– and sweating! Unlike Tina Turner– who wears leather that doesn't absorb sweat– my puffy shirt and tuxedo made me look like a drowning cat. At times, my glasses would even fog up. I think I lost about 10 pounds of sweat each performance. Do you think I became dehydrated?

First, to be clear: dehydration is not the same as hypovolemia– decreased body fluid volume. For example, in Monty Python and the Holy Grail, the Black Knight becomes hypovolemic when he has all his limbs cut off and blood is squirting everywhere. His body fluids are low, and so his blood pressure drops and his organs don't get enough blood.

On the other hand, dehydration means low free water.  You can be dehydrated from sweating too much and not drinking enough. When the body is low in water, the serum sodium level increases. This triggers the brain to release antidiuretic hormone (ADH) to tell the kidneys to reabsorb more water back into the body– which helps preserve body fluid volume.

The brain also signals, "Hey! I'm thirsty!" So you drink more water to stay hydrated. (There are other mechanisms too, but let's just focus on this one.)

We all lose water from our bodies like the government spends our tax dollars. Poof! It's gone! We lose water in our breath (exhale on a cold window and see the moisture from your lungs). Skin releases water, especially when it's hot outside or you're exercising. Water is lost during a bowel movement, especially with diarrhea. 

"Water, water, everywhere, and all the boards did shrink; water, water, everywhere, nor any drop to drink" said the ancient mariner.

 So how much water should a person drink? That's the $64,000 question, because it really varies depending on a body, habits, age, condition, etc. If you drink too little, your sodium levels can increase to dangerous levels. If you drink too much, your sodium levels can decrease to dangerous levels. (Yes, even water can be toxic at high levels. If it's not one thing, it's another, Blanche.)  

Assuming everything's working properly, you'll know when you need water because you'll be thirsty, and the thirst will stop when you're hydrated enough. Generally speaking, normal adults need at least 1600cc of water a day. 

Water comes in fruits and vegetables as well as from the tap. The movie Like Water for Chocolate might mislead you to think eight bars of Lindt are equivalent to eight glasses of water, but they aren't– too bad! 

I drink plain old tap water that's filtered. Honestly, I don't understand why everyone loves bottled water– it hasn't been proven to be any better for you, it's expensive, and some manufacturers actually add extra calories and "stuff" to it.

It just seems to me that people who buy that stuff have water for brains.